Preparation of synthetic lubricant



Patented Sept. 1?, 1950 Denham Harman and William E.

Vaughan,

Berkeley, Calif., assignors to Shell Development Company, San Francisco, Calif., a corporation of Delaware I i No Drawing. Application October 5, 1946, Serial No.

10 Claims. (Cl. 260-609) I This invention relates to novel lubricating compositions. More particularly, it pertains to the use of certain fractions of non-mineral oil base sulfur-containing compounds, especially for low temperature and/or extreme pressure lubrication.

The use of mineral oil fractions for lubricating is suitable for many purposes, but it is welllmown that such lubricants possess certain inherent limitations, such as tendency to oxidize, thickening at low temperatures, etc. A large number or additives have been employed with mineral oils in order to improve these shortcomings. To a certain degree, the resulting compositions may be used successfully for most lubricating purposes. 1

Various synthetic lubricants have been proposed from time to time. These include polymers of cracked wax oleflns, alkylated aromatics and so on. Some of these are useful for special purposes, but, especially if the previously known synthetic lubricants were derived from oleflnic sources, they usually possessed corrosion and oxidation characteristics limiting their utility to a substantial degree. Another type of synthetic lubricant which has been investigated is the alkylene oxide polymer type, such as polymerized propylene oxide. I

-The preparation of adducts of certain unsaturated compounds with hydrogen sulfide or mercaptans has also been proposed. However, especially when reacting hydrogen sulfide with dioleflns, a complicated mixture of derivatives is present in these adduct products. The mixtures prepared by previously proposed methods contain relatively large proportions of volatile constituents as defined hereinafter, with a correspondingly lower proportion having lubricating properties, dependent upon the identity and' quantity of catalyst employed.

It is an object of the present invention to provide a novel method for the production of a nonhydrocarbon lubricant. It is another object of the present invention to provide a novel method for the preparation of a lubricant useful at low temperatures. It is still another object of this invention to provide a novel method for the preparation of a lubricant possessing inherent extreme pressure properties. Other objects will become evident from the following disclosure.

Now, in accordance with this invention, it has been found that the lubricant adducts of unsaturated organic compounds, especially those containing olefinic linkages, with such sulfurbearing substances as hydrogen sulfide or mercaptans, may be produced in yields substantially higher than by previously known methods, by using a peroxide to catalyze the formation of the adduct.

The unsaturated organic compounds from which the lubricant may be prepared possess at least one unsaturated linkage between two alipliatic carbon atoms regardless of the character of the compound embracing such a linkage. The unsaturated hydrocarbons, such as the oleflns, which term is intended to include poly-olefins and olefin polymers, are particularly contemplated. Examples of unsaturated hydrocarbonsclude substituents such as alkoxy, alkenoxy, aryloxy, alkaryloxy, aralkyloxy, alkylimido, etc. As examples, reference may be made to methylacrylate, methyl-methacrylate, divinyl ether, diallyl ether, dimethallyl ether, allyl alcohol, diallyl sulfide, diallyl disulflde, and the like.

The lubricants prepared according to the present invention are especially versatile if the unsaturated compound has terminal aliphatic unsaturated linkages. The unsaturated ethers such as diallyl ether and divinyl ether meet this latter requirement and are a. preferred class of substances useful in the preparation of the lubricants of the present invention. One group of such unsaturated ethers comprises the aliphatic oxyethers in which only one of the aliphatic radicals attached to the ether oxygen atom contains an unsaturated linkage. Examples of such ethers are ethyl vinyl ether, ethyl propenyl ether, methyl isopropenyl ether, ethyl isopropenyl ether, methyl allyl ether, ethyl allyl ether, n-propyl allyl ether, isopropyl allyl ether, 4-ethoxybutene-l, G-ethoXy-hexene-I, gamma-ethoxyalpha-butylene, methyl propargyl ether, ethyl propargyl ether, etc., and their homologs and analogs. The above unsaturated ethers and their homologs may be substituted by straight-chain, cyclic and/or heterocyclic radicals, as well as by as halogens.

bon atoms include divinyl sulfide, .chlorovinyl) thioether, diallyl sulfide, dicrotyl Another group of suitable unsaturated ethers which may be employed as a startingmaterial in one oi' the radicals attached to the thioether sul-- fur atom contains an unsaturated linkage. Examples of this group are ethyl vinyl sulfide, ethyl isopropenyl sulfide, and the like.

While suitable lubricants may be prepared from the above types of unsaturated ethers, it is preferred that both radicals attached to the ether oxygen or thioether sulfur groups contain unsaturated (preferably olefinic) linkages, since'the adducts formed therefrom usually contain a relatively large fraction having superior lubricating properties. The following are illustrative examples of such poly-unsaturated ethers: divinyl ether, diisopropenyl ether, diallyl ether, dicrotyl ether, dimethallyl ether, di(alpha-methyl-allyl) ether, (butene-1-yl-3) (butene-2-yl-4) ether, dihexenyl ethers, allyl(2-methyl-pentene-1-yl-2) .ether, allyl linalyl ether, etc., as well as the haloin which each radical attached to the sulfur atom contains an unsaturated linkage between two cardi(betasulfide, dimethallyl sulfide, dihexenyl sulfides, and the like, and their homologs and analogs.

The ethers employed as the starting material for the preparation of the present lubricants may also contain more than one ether oxygen atom and/or thioether sulfur atom, this group of unsaturated ethers being represented by compounds of the type 'of 1,2-bis(vinyloxy) ethane, 1,3-bis- (vinyloxy) propane, 1,2-bis(allyloxy) ethane, and the like, as well as by the unsaturated disulfides,

such as divinyl disulfide.

At times, especially for extreme pressure lubricant purposes, it is highly desirable that a halogen-containing lubricant be employed. For this purpose, in accordance with the present invention, lubricants may be prepared from adducts, involving a halogenated unsaturated organic compound. Such halogenated unsaturated compounds may contain one or more oleflnic linkages, preferably of olefinic character. These compounds may contain one or more halogen (i.e. chlorine, bromine, iodine land/or fluorine) atoms which may be attached to saturated or unsaturated carbon atoms of the compound.

Examples of such halogenated hydrocarbons are: vinyl halides, allyl halides, z-halo-propylene, crotyl halides, isocrotyl halides, 4-halo-butene-1 methallyl halides, 2-halo-butene-2, monohalogenated acetylenes, propargyl halides, 1,1-dihaloethylenes, trihalo-ethylenes, 2-halo-pentene-1, 3-halo-cyclohexane, 2 halo-1,4 diphenyl butene-2,3-halo-pentadiene-l,4, and their homologs. The above class of halogenated compounds may be further substituted in the nucleus and/or in the substituents in various degrees by straightchain, branched chain, carbocyclic, and/or heterocyclic radicals, and by such substitutents as alkoxy, alkenoxy, arylow, alkylimido, and the like. Also, the organic compounds of the'above class may contain two or more halogen atoms which may be attached to saturated and/or unthe present lubricants are derived are formed by reaction of one or more of the above unsaturated organic compounds with hydrogen sulfide or a Any sufliciently stable aliphatic haercaptan is suitable as a reactant for the formation of such adducts. A suitable aliphatic mercaptan may contain one or more sulfhydryl groups or radicals, preferably dior polymercaptans. In the majority of cases it is preferable to employ mercaptans of primary, secondary or tertiary character, particularly those contained or derived from petroleum or petroleum products. The methyl, ethyl,

-buty1, amyl, hexyl, heptyl, octyl and the like mercaptans as well as their homologs, analogs and substitution products, may be employed with excellent results.

The formation of adducts of unsaturated organic compounds and hydrogen sulfide or mercaptans in the presence of peroxides proceedsaccording to the mechanism in which the sulfur of the mercapto or sulfhydryl group attaches predominately to the unsaturated carbon atom holding the most hydrogen atoms.

This type of addition is termed abnormal," since it takes place contrary tothe course suggested by the Markownikoil rule. The abnormal" addition previously has been catalyzed by the actinic radiations. This reaction is seriously limited in many cases by non-chain initiating absorption of actinic radiation. The abnormal addition is in accordance with the rule proposed by Posner (Berichte 38,646. (1904)). Now it has been discovered, in accordance with the present invention that organic peroxides are an outstanding group of sensitizers for the purpose of producing lubricants, under proper conditions, since an exceptionally large proportion of the product so derived has lubricating properties.

- The reaction is carried out by heating the unsaturated organic compound and hydrogen sulfide or a mercaptan in the presence of an organic peroxide, preferably in a closed vessel.

The peroxides preferably are organic peroxides such as the alkyl hydroperoxides, dialkyl peroxides, and alkvlperoxy hydrocarbon derivatives.

The alkyl hydroperoxides form a preferred group of catalysts, and of these the tertiary-alkyl hydroperoxides are the most active. These include tertiary-butyl hydroperoxide, tertiary-amyl hydroperoxide, tertiary-hexyl hydroperoxide, etc. An especially preferred class of peroxides are the dialkyl peroxides, and of these, the di-tertiaryalkyl peroxides are the most satisfactory. This group is exemplified by di-tertiary-butyl peroxide, di-tertiaryamyl-peroxide, di-tert-hexyl peroxide, etc.

Other peroxides which act as catalysts include alkyl peroxy alkanes, such as 2,2-bis(tertiarY- butylperoxy) butane, as well as peroxides such as benzoyl peroxide, aeetyl peroxide, benzoyl acetyl peroxide, and lauroyl peroxide, and hydroxyalkyl peroxides, such as hydroxy methyl tertiary butyl peroxide.

The peroxide catalyst may be used in a wide range of concentration, but preferably is present in amounts from about 1 mol per cent to about 10 mol per cent, based on the total mols of reactants present. Optimum results are obtained when the catalyst concentration is from about 2 to about 5 mol per cent.

The ratio of unsaturate to hydrogen sulfide or mercaptan may vary within relatively wide limits, but preferably is between 0.5 and 2 mols unsat urate to 1 mol hydrogen sulfide or mercaptan.

The temperature at which the reaction is conducted will depend to a certain extent on the concentration, activity and stability of the peroxide mercaptan in the presence of an organic peroxide, 7; If temperatures above C. are used when the catalyst concentration is as high as mol per cent, the reaction may become violent even to the point of explosion, However, if an active peroxide is present, even inamounts as low as about one mole per cent, the reaction will proceed at a, satisfactory rate at temperatures as low as about 40 C. It is preferable, from an economic and control standpoint, and when using about 2% mol per cent of a catalyst of the activity of di-tertiary-butyl peroxide, to maintain the temperature within the range from about 100 C. to about 140 C. The time for which the adduct reaction is allowed to proceed willvary with the activity of the catalyst and the temperature being employed. Usually the reaction will be completed when the other conditions are as stated hereinbefore, in from about 1 to about 48 hours, and close control of the reaction is obtained when conditions are such that the reaction time is from about 2 toabout 10 hours. Diluents may or may not be used, as desired. While they are not essential, their use at times may be preferable in order to reduce the viscosity of the reaction mixture, to act as a mutual solvent i'or the reactants and catalyst, or to reduce the concentration of the reactants, thus allow- 8 close control oLthe course of the reaction. Preferably, the diluent is substantially inert with respect to the reactants or catalysts. Saturated hydrocarbons or chlorinated saturated hydrocar bons are useful for this purpose. However, ra active diluents may be used for the purpose of initiating or terminating polymer chains, sons to give adducts having modified propertiesfa's, more particularly pointed out hereinafter, v,

The reaction proceeds at its optimum rate when retardants such as hydroquinor'ie,Lpiperi-w dine, and certain metal salts are absent. ,Upon 40" completion of the formation of the adduct, the product is further treated to eliminate that fraction of the product which is too volatile, or other- I wise unsuitable, for use as a lubricant. Thistreatment may vary with ,-the product and the type of lubricant desired, but usually comprises selective solvent extraction for the removal of catalyst and undesirable fractions, or partial distillation, usually under diminished pressure, or a combination of these two steps.

An essential feature a of" the I present invention is the substantially complete removal "of the volatile components ofthe adduct. Since the adduct reaction usually results in the formation of a mixture of products of continuously varying molecular weight, this relatively volatile fraction will vary in'amount,dependentupon'the conditions under which the adduct is;formed. The sensitizer employed and" its amount will havea great effectupon the prjportion "of relatively volatile components in the "product. '1 v When peroxidesare used to; catalyze the for-f mation of the adduct, it" has been found, inac I cordance with'this invention, that theprop'ortionj of fractions having lubricating'properties'is unusually high, as compared with 'the yield obtained whenother catalysts areemployed: 1 a P The fraction of,relatively yolatile constituents removed will depend upon, the lubricating ;.pu rpose for which theremainder will be employed. If no fraction" removeame composite 'adduct is generally 'useles'sf as a lubricant; 1" since ftheji li hter fractions will inevitably volatilize -mg a lubricationoperation'to a greater or less "def gree, dependentu on the conditions to which the adduct is subjected. 7 However, for general?! :wherein it and: mi i ates 1 produce, greases: manic s B a lubricating purposes, the fraction volatilizing below about C. at 0.2 cm. mercury pressure is preferably removed, and generally, that fraction volatilizing below about C. at 0.2 cm. mercury pressure is removed in order to obtain a lubricant having optimum properties.

The lubricant so obtained may be further treated in order to improve color, alter terminal" groups, etc, if desired.

ing an unsaturated linkage. I

When ethers or thioethers having linkages in both radicals attache oxygen or thioether sulfur atom are hydrogen sulfide or a mercaptanijas rib hereinbefore, the adducts"'are"'poiymeric""coni Pounds having units of a q .1

,. .1112 401-... xvsen,v den de t upon whe he ..1anether or;a thioetherawasaiusedl and ea h" R21 s. v i: or anic radical saturated hydrocarboniradical .571 3;,-

when the adduct is formed from hydrogen sulfide and an oxyether having unsaturated linkages inbothradicals attached to the ether oxygen atom; -th polymer has the general formula e or, different dijoriunsubstitutedihydrocar ntradicals, mv is an integer,. R1 represents thehydrogen atom or radicals 'SllGh.%flS-.7CH2+R&-Q-R6,::.R4 represents the sulfhydryl radical or radicals sucn=as +fls+ cmenjg+o mecns"wh rein-R5 through narepresennikeor diiferent substituted or unsubstituted hydroca,rbonv radicals. out-.- standin'gfimember of thisi fg'rallpl lis' the 'adduct of diallyletherjandfhydrogenf ,sulfide. m W eelsrflfl a u a edh h s r ii d i hydrogedsulilde, th'e polymer corresponds" to that above, except that the oxygen'ato'm's are' all replacedby sulfur. atoms, wthus'g; giving, a. I polymer having a high sulfur, content; especially useful for extreme pressure, lubrication. 2,: An out-v standing member of this groupis the adduct of diallylsulfide and hydrogen sulfide. The adducts, formed according to the method of the present invention-:areuparticularlyuseful in the preparation of lubricants, since the use of peroxide .catalysts' enables the" 'prodi'iction or alarge fraction hav'irig .i-lubrica'.tin'g Lpmperties.

The adducts so formed are. stable to oxidation in anti-oxidants; Such;

and respond "well to co exceptional extreme pressure characteristics, They may be used bythems'elve's as lubricants, or may be added to other lubricant bases, such "as mineral oils, polymeric alkylene oxides or corrosion compositions, jetc.j a suitable for,.use in cutting "oil' combos The following" exa j'ill 'ratet of the prestniiiiven adducts so prepared:

I a aaaasia 7 exam-s r---rnaoxmn CATALYZED and diallyl ether, together with 5 mol percent di-tertiary-butyl' peroxide were heated in an autoclave at 100 C. for 30 hours. Following adduct formation, the more volatile-fractions were removed by fractional distillation at subatmospheric pressure. The fraction of the product boiling above 240 C. at 0.2 cm. mercury pressure (70% of the charge) had the following properties:

Viscosity centistokes at 100 F 77.0 Viscosity, centistokes at 210 F.- 13.0 Viscosity inde 1 .143 S. A. E. gra 30 Pour point, 60

EXAMPLE II.-PEROXIDE CATALYZED ADDUCT OF H25 AND DIALLYL ETH'ER Adducts were prepared as described in Example I, using several different peroxides, heating for 20 hours at 65C. The yields of product boiling above 160 C. at 0.2 cm. mercury pressure are given in Table 1, below.

Tabl I Lubricant Fraction 2,2-bls(tertiary-buty1pero )bntane.-- 30 tertiary-Butyi hydropero do i 67 my] pnmrirln 25 Benzoyl peroxide 20 1 Reaction mixture heated 30 hours at 100 0.

EXAIVIPLEi III.LAUSON ENGINE TEST ON HaS-DIALLYL ETHER- ADDUCT The adduct prepared as described in Example I was tested as a lubricant in a standard Lauson engine, operated at a Jacket temperature of 100 F. for 40 hours. The following characteristics were observed:

Bearing weight loss, mgs. per sq. cm.-- 7.3

. 011 consumption Normal Sludge deposits None Ring belt depositsm. Medium Wear Normal Approximate S. A. E. grade 20-.

Percent viscosity increase during test 42 EXAIVIPLE IV.-WEAR TEST-ES ADDUCTS OF DIALLYL ETHER Two adducts of hydrogen sulfide and diallyl ether, were tested for wear characteristics in the four-ball wear apparatus described by Boelage in Engineering (June 14, 1933). Results of the test are given in Table 2 below.

At 80 0., 1200 R. P. M., 15 kg. load: Average diameter or wear scar, mm. 0.25 Coeflicient oi friction 5 seconds 0.056 Coefllcient of friction average of 30, 40, 50 and 80 sec 0.054 At 130 C., 1200 R. P. M., kg.

load: Average diameter or wear scar, mm 0.26 Coeiiicient of friction after 5 seconds Coefficient of friction average 01' 30, 40, 50 and 60 sec 0.043 At 30 C., 700 R. P. M., 7 kg. load,

two hour test:

Sear diameter, mm. 0.40 Average coefllcient of friction during the 2 hr. test"... 0.081 At 80 C., 700 R. P. M., 7 kg. load,

2 hour test:

Scar diameter, mm. 0.48 Average coemcient oi friction during the 2 hr. test 0.058 At 130 C., 700 R. P. M., 7 kg. load,

2 hour test:

Scar diameter, mm. 0.33 Average coeflicient of friction during 2 hr. test 0.073 0.080

EXAIMPLE V.-THERMAL STABILITY OF THE HaS-DIALLYL EI'HER ADDUCT The adduct prepared as described in Emmple I was heated for 24 hours at 150 C. in a carbon dioxide atmosphere in order to determine what changes occur in its properties in the absence of oxidizing influences. Table 3 presents the data 5 EXAMPLE ill-OXIDATION STABILITY OF HaS-DIALLYL ETHER ADDUCT Seventy-five grams of the adduct of diallyl ether and hydrogen sulfide, prepared as described in Example I were heated at 140 C. in the presence of 1 sq. cm. copper per gram oil under an initial oxygen pressure of 50 p. s. i. It ree quired 11.5 hours heating under these conditions for the oxygen pressure to drop 10 p. s. 1., and 26 hours for the pressure to drop 20 p. s. 1.

EXAMPLE VIL-EX'I'REME PRESSURE LU- BRICATING PROPERTIES OF THE Has-DI- ALLYL E'I'HER ADDUCI' The adduct prepared as described in Example I was tested under loads simulating extreme pressure lubricating conditions, using the four-bail machine described by Boelage in Engineering (June 14, 1933). Table 4 presenis the data ob- 75 tained.

We claim as our invention:

1. The process which comprises heating hydrogen sulfide and diallyl ether in the presence of a minor amount of di-tertiary-butyl peroxide at a temperature from 40 to 150 C. for a period between one and 48 hours and removing from the mixture of polymeric adducts so formed the fraction volatilizing below 160 C. at 1 cm. mercury pressure.

2. The process which comprises heating hydrogen sulfide and diallyl ether in the presence of a dialkyl peroxide at a temperature between 40 and 150 C, and removing from the mixture of linear polymeric adducts so formed the fraction volatilizing below 160 C. at 1 cm. mercury pressure.

3. The process which comprises heating hydrogen sulfide and a dialkenyl ether in the presence of a catalyst of the group consisting of dialkyl eroxides and alkyl hydroperoxides, and removing from the mixture of linear polymeric adducts so formed the fraction volatilizing below 160 C. at 1 cm. mercury pressure.

4. The process which comprises heating a sulfur compound having the general formula wherein both Rs are of the group consisting of hydrogen atoms and alkyl radicals, at least one R being a hydrogen atom, with a dialkenylether, in the presence of a minor amount of a catalyst of the group consisting of dialkylperoxides and alkyl hydroperoxides, whereby a mixture of polymeric linear adducts of the reactants is formed, and subsequently removing from said mixture the fraction which volatilizes below 160 C. at 1 cm. mercury pressure.

5. The process which comprises heating an alkyl mercaptan with a dialkenyl ether in the presence of a minor amount of a catalyst of the group consisting of dialkyl peroxides and alkyl hydroperoxides, whereby a mixture of polymeric linear adducts oi the reactants is formed and subsequently removing from said mixture the fraction which volatilizes below 160 C. at 1 cm. mercury pressure.

6. The process which comprises heating a sul- 60 fur compound having the general formula R-S-R B being a hydrogen atom, with a dialkenyl ether in the presence of a minor amount of a dialkyl peroxide, whereby a mixture of polymeric linear adducts of the reactants is formed and subsequently removing from said mixture the fraction which volatilizes below C. at 1 cm. mercury pressure.

'7. The process which comprises heating a sulfur compound having the general formula wherein both Rs are of the group consisting of hydrogen atoms and alkyl radicals, at least one R being a hydrogen atom, with a dialkenyl ether in the presence of a minor amount of an alkyl peroxide, whereby a mixture of polymeric linear adducts of the reactants is formed and subsequently removing from said mixture the fraction which volatilizes below 160 C. at 1 cm. mercury pressure.

8. The process which comprises heating hydrogen sulfide having a dialkenyl ether in the presence of a dialkyl peroxide catalyst and removing from the mixture of linear polymeric adducts so formed, the fraction volatilizing below 160 C. at 1 cm. mercury pressure.

9. The process which comprises heating hydrogen sulfide having a dialkenyl ether in the presence of an alkyl. hydroperoxide catalyst and removing from the mixture of linear polymeric adducts so formed, the fraction volatilizing below 160 C. at 1 cm. mercury pressure.

10. The process which comprises heating hydrogen sulfide and divinyl ether in the presence of a catalyst of the group consisting of dialkyl peroxides and alkyl hydroperoxides and removing from the mixture of linear polymeric adducts so formed, the fraction volatilizing below 160 C. at 1 cm. mercury pressure.

DENHAM HARMAN.

E. VAUGHAN.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,197,781 Badertscher et al. Apr. 23, 1940 2,319,183 Badertscher et al. May 11, 1943 2,352,435 Hoeifelman et a1. June 27, 1944 2,373,343 Rummelsburg Apr. 10, 1945 9 ,295 Rust et a1 Jan. 1, 1946 OTHER REFERENCES Jour. of A. C. S. (1938) 60: 2452 to 2455.

Chem. Rev. (1942) 27: 388 to 394.

Vaughn et al.: Jour. Organic Chem., vol. 7, pages 472-6 (1942).

Jones et al.: Jour. Am. Chem. Soc., vol. 60, page 2452 (1938).

Kharasch et al.: Chemistry and Industry, vol. 5'7, page 752 (1938) 

1. THE PROCESS WHICH COMPRISES HEATING HYDROGEN SULFIDE AND DIALLYL ETHER IN THE PRESENCE OF A MINOR AMOUNT OF DI-TERTIARY-BUTYL PEROXIDE AT A TEMPERATURE FROM 40* TO 10*C. FOR A PERIOD BETWEEN ONE AND 48 HOURS AND REMOVING FROM THE MIXTURE OF POLYMERIC ADDUCTS SO FORMED THE FRACTION VOLATILIZING BELOW 160*C. AT 1 CM. MERCURY PRESSURE. 